• chronic proliferative rhinitis
• prevalence
• Salmonella enterica
• sheep
• slaughterhouse
• Tuscany

Salmonella enterica subsp. diarizonae serovar 61:k:1,5,(7) (SED) is a recognised commensal of sheep and the aetiological agent of chronic proliferative rhinitis (CPR). However, its prevalence in the upper respiratory tract of clinically healthy animals remains poorly characterised. This cross-sectional study estimated the nasal carriage rate of SED in slaughtered sheep from commercial flocks in Tuscany (Italy) and assessed the potential implications for animal and public health.
Between February and May 2025, 100 nasal swabs were obtained at a single abattoir from adult sheep (> 18 months) originating from five provinces (Lucca = 16, Florence = 15, Grosseto = 8, Livorno = 12, Pisa = 49). The cohort was predominantly female (98 %) and comprised Sarda (37 %), Massese (31 %) and Lacaune (22 %) breeds. Swabs were cultured on selective media, presumptive colonies were confirmed biochemically, and molecular identity was verified by PCR targeting the sfrC gene.
Sixteen swabs yielded SED; positive animals originated from four of the five provinces sampled. None of the carcasses exhibited macroscopic lesions consistent with CPR. Although the prevalence observed is lower than the 45 % nasal-plus-faecal carriage recently reported in Spain, it corroborates the nasal cavity as a silent reservoir and is consistent with the 43 % tonsillar colonisation documented in Switzerland.
The detection of asymptomatic carriers at slaughter highlights the slaughterhouse as an epidemiological observatory and justifies targeted on-farm control measures together with reinforced hygiene during head handling and evisceration. Longitudinal studies incorporating larger sample sizes, additional anatomical matrices (tonsils and faeces) and whole-genome sequencing are warranted to clarify shedding dynamics, antimicrobial-resistance profiles and clonal relationships among ovine, environmental and occasional human isolates. Such evidence will be pivotal for developing cost-effective, risk-based surveillance within a One-Health framework.